Ducklow, H. W., W. R. Fraser, M. P. Meredith, S. E. Stammerjohn, S. C. Doney, D. G. Martinson, S. F. Sailley, O. M. Schofield, D. K. Steinberg, H. J. Venables and C. D. Amsler, 2013: West Antarctic Peninsula: An Ice-Dependent Coastal Marine Ecosystem in Transition. Oceanography, 26(3): 190-203.
The extent, duration, and seasonality of sea ice and glacial discharge strongly influence Antarctic marine ecosystems. Most organisms' life cycles in this region are attuned to ice seasonality The annual retreat and melting of sea ice in the austral spring stratifies the upper ocean, triggering large phytoplankton blooms. The magnitude of the blooms is proportional to the winter extent of ice cover, which can act as a barrier to wind mixing. Antarctic krill, one of the most abundant metazoan populations on Earth, consume phytoplankton blooms dominated by large diatoms. Krill, in turn, support a large biomass of predators, including penguins, seals, and whales. Human activity has altered even these remote ecosystems. The western Antarctic Peninsula region has warmed by 7 degrees C over the past 50 years, and sea ice duration has declined by almost 100 days since 1978, causing a decrease in phytoplankton productivity in the northern peninsula region. Besides climate change, Antarctic marine systems have been greatly altered by harvesting of the great whales and now krill. It is unclear to what extent the ecosystems we observe today differ from the pristine state.
Hays, J. D., D. G. Martinson and J. J. Morley, 2013: Biological and climatic consequences of a cold, stratified, high latitude ocean. Quaternary Science Reviews, 82: 78-92.
The flux from deep- and shallow-living radiolarian assemblages provides evidence of a glacial, high latitude, cold ocean stratification that increased biological pump efficiency and promoted ocean carbon sequestration. Greater deep (>200 m) than shallow-living (<200 m) radiolarian assemblage flux characterizes glacial North Pacific (>45 degrees N) sediments with the deep-living Cycladophora davisiana dominant (>24%). By contrast modern radiolarian flux consists primarily of shallow-living species (C davisiana <10%). Clues to the cause of this unusual glacial radiolarian flux come from the presently, strongly stratified Sea of Okhotsk. Here beneath a thin nutrient depleted mixed layer radiolarian and zooplankton faunas conform to the sea's physical stratification with lower concentrations of both in a Cold (-1.5 to 1 degrees C) Intermediate Layer (CIL) (20-125 m) and higher concentrations in waters between 200 and 500 m (Nimmergut and Abelmann, 2002). This biological stratification generates a radiolarian flux echoing that of the glacial northwest Pacific with C davisiana 26% of total flux. Widespread C davisiana percentages (>20%) in high latitude (>45 degrees) glacial sediments of both hemispheres is evidence that these oceans were capped with an Okhotsk-Like Stratification (O-LS). O-LS provides mechanisms to (1) strip nutrients from surface waters depriving the deep-ocean of preformed nutrients, increasing biological pump efficiency and (2) deepen carbon re-mineralization increasing deep-ocean alkalinity. Both may have contributed to lower glacial atmospheric CO2 concentrations. O-LS would also have amplified glacial climatic cycles by promoting the spread of high latitude sea ice in winter as occurs in the Sea of Okhotsk today, and reducing gas exchange between ocean and atmosphere in summer. (C) 2013 Elsevier Ltd. All rights reserved.
The database was updated today.